Alternative Reuse of Oligomers Derived from Poly(ethylene terephthalate) Waste Deposited onto Microspheres and Determination of Adsorbent Properties Toward Toxic Metals

The aim of this work is to report the alternative reuse of poly(ethylene terephthalate) waste based on the preparation of oligomers by catalyzed glycolysis, their deposition onto the surface of stainless steel metallic hollow microspheres and the determination of adsorbent properties toward lead, nickel and cadmium cations in aqueous solutions. The coated microspheres were characterized by field emission scanning electron microscopy, differential scanning calorimeter and energy-dispersive X-ray spectroscopy. In the case of oligomers, they were also characterized by infrared spectroscopy, gel permeation chromatography and 1H NMR analyses. The adsorption properties of coated microspheres toward toxic metals showed maximum adsorption capacities of 309.32, 225.35 and 97.72 mg g−1 for lead, nickel and cadmium cations, respectively; which fitted very well with the Freundlich isotherm model. In a preliminary fixed-bed column study based on the removal of heavy metals by means of the coated microspheres showed that breakthrough curve for the Pb2+ presents the better fitting to the experimental data at times greater than 30 min and predicts the equilibrium at time greater than 160 min. Adsorption/desorption studies demonstrated that coated microspheres could be recovered using 0.05 M EDTA solution with a maximum recovery amount of heavy metals higher than 50%, which making them regenerable and reusable. These results suggest that coated stainless steel metallic hollow microspheres with oligomers obtained from PET waste are a potential system for the removal of heavy metal from contaminated effluents.